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Intrusive rocks also exist in a wide range of forms from mountain range sized batholiths to thin vein-like fracture fillings of aplite. Structural types include:

• batholith: large irregular intrusions.
• stock: smaller irregular disordant intrusions.
• dike: a relatively narrow tabular discordant body with near vertical attitude.
• sillIn geology, a sill is a tabular, horizontal mass of igneous rock that has been intruded laterally between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term "sill" is syn: a relatively thin tabular concordant body intruded along bedding planes, horizontal attitude.
• pipe or volcanic neck: circular or tube shaped nearly vertical body which may have been a feeder vent for a volcano.
• laccolithA laccolith is any of a type of igneous intrusion (or concordant pluton) that has been injected between two strata of a sedimentary bed. The pressure of the magma is high enough that the overlying strata are forced upward, giving the laccolith a dome or m: concorant body with essentially flat base and dome shaped upper surface, usually has a feeder pipe below.

Diapir is the more general term for intrusions that includes both igneous and non-igneous structures, such as salt domeA salt dome is formed when a thick bed of evaporite minerals (mainly salt, or halite) found at depth intrudes vertically into surrounding rock strata, forming a diapir. The salt that forms these deposits was laid down in prehistoric times, mainly in places. A diapir is any relatively mobile mass that intrudes into preexisting rock strata. Diapirs commonly intrude vertically through more denseFor other meanings of density, see density (disambiguation Density (symbol: rho Greek: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The average density of an object equals its total mass div rocks because of buoyancyIn physics, buoyancy is an upward force on an object immersed in a fluid, enabling it to float or at least to appear to become lighter. If the buoyancy exceeds the weight, then the object floats; if the weight exceeds the buoyancy, the object sinks. It wa forces associated with relatively low-density rock types, such as salt, shale and hot magma, all of which form diapirs. The process is known as diapirism.

By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping petroleumNodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petrus rock and oleum oil), mineral oil or crude oil sometimes colloquially called black gold is a thick, dark brown or greenish flammable liquid, which exists in the uppe and natural gasNatural gas is a gas produced by the anaerobic decay of organic material. It is usually found in oil fields and natural gas fields, but is also generated in swamps and marshes (where it is called swamp gas or marsh gas , in landfill sites, and during dige. Igneous intrusions themselves are typically too hot to allow the preservation of preexisting hydrocarbons.